Engineered Strains for Optimized Bacterial Protein Expression

Merck’s portfolio of bacterial strains for protein expression includes the best all-purpose strains and several specialty strains for difficult-to-express proteins, all backed by unwavering technical support to increase your chances of success. For ultimate convenience and reliability in plasmid transformation, Singles™ Competent Cells are provided in 50 μL volumes to eliminate the need to aliquot, freeze/thaw, or waste partially used vials. This saves time, money, minimizes contamination and ensures reliable cell performance.

BL21(DE3) Singles™ Competent Cells

BL21 has been the gold standard for protein expression since it was first introduced in 1990. Deficient in Lon and OmpT proteases, BL21 and its derivatives are ideal for many applications. T7 expression strains are lysogens of bacteriophage λDE3, as indicated by the (DE3), and carry a chromosomal copy of the T7 RNA polymerase gene under control of the lacUV5 promoter. Such strains are suitable for production of protein from target genes cloned in appropriate T7 expression vectors.

Overnight Express Protocol

The Overnight Express™ Autoinduction Systems enable regulated protein expression in E. coli, without monitoring the culture or adding inducer during cell growth. The simplified protocol offers great convenience, allowing you to focus on your research while it does its job. Learn more about our overnight express protocol.